This invention relates to antimicrobial compositions containing free fatty acids and to pharmaceutical formulations containing same.
Free fatty acids are essentially insoluble in water. Their insolubility and the fact that they are incompatible with many conventional excipients have seriously restricted their medicinal use to date. While salts of free fatty acids are soluble in water, they are known to have greatly reduced antimicrobial effect. Several methods have been used to “solubilise” free fatty acids, including the use of alcohols and surfactants and derivitisation by re-esterification to form mono-glycerides and/or ethoxylation and propoxylation procedures.
The antimicrobial properties of free fatty acids have been known for many years (Kabara J. et al. Antimicrobial Agents and Chemotherapy, July 1972; 2(1): pp 23-28).
Bergson et al. (Antimicrobial Agents and Chemotherapy, November 2001, pp 3209-3212), reported that both capric and lauric acid were effective in killing the yeast Candida albicans. 
Sun et al. (Chemico-Biological Interactions 140 (2002), pp 185-198), identified the superior microbicidal properties of caprylic, capric and lauric acid, concluding that lauric was most potent against gram positive bacteria while caprylic was optimal against gram negative organisms.
The anti-viral properties of free fatty acids were reported by Halldor et al. (Antimicrobial Agents and Chemotherapy; January 1987, pp 27-31).
WO 03/018049 discloses the antimicrobial activity of milk serum apo-proteins in combination with free fatty acids from milk fat. It is illustrated that the adhesion inhibitory properties of milk extracts are exclusively attributable to the water soluble protein fraction, and that the lipid component makes no contribution to this effect.
WO 2009/072097 discloses properties of compositions of free fatty acids such as melting point depression and sequestration which affect antimicrobial potency. Also disclosed are emulsification methods used to incorporate blends of free fatty acids in a milk whey protein isolate.
Sprong et al. (Antimicrobial Agents and Chemotherapy, Vol 45, No 4, 2001, pp 1298-1301), report microbicidal effects for sphingosine and sphingomyelin and some slight effect from lyso-phosphatidyl ethanolamine and lyso-phosphatidyl choline, but no effect was observed from any of the unmodified phopsholipids. It is notable that these results are reported for exposure times in excess of 2 hours at 37° C., in contrast to the present invention where microbicidal effects are shown for combinations of membrane lipids and free fatty acids, for exposure times of less than 5 minutes.
Jones et al: Journal of Pharmacy and Pharmacology, 2003, Vol 55, No 1. pp 43-52 discloses the use of lecithin in combination with cholesterol as a surface coating to inhibit bio-film formation on medical devices.
It is an object of the invention to provide improved antimicrobial compositions containing free fatty acids.